Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Supramolecular aggregates formed by sulfadiazine and sulfisomidine inclusion complexes with a- and b-cyclodextrins N. Rajendiran ⇑, G. Venkatesh, J. Saravanan Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
SDA/a-CD complex self assembled to
formed hierarchal morphology. SDA/b-CD and SFM/b-CD complexes
self assembled to form the nanosheet. SFM/a-CD complex self assembled to
form nanoporous sheet. van der Waals, hydrophobic and
hydrogen bonding interactions play a vital role in the self assembling process.
a r t i c l e
i n f o
Article history: Received 1 December 2013 Received in revised form 5 March 2014 Accepted 18 March 2014 Available online 28 March 2014 Keywords: Sulfa drugs Cyclodextrins Inclusion complex Self assembly Nanosheet Nanomaterial
a b s t r a c t Sulfadiazine (SDA) and sulfisomidine (SFM) inclusion complexes with two cyclodextrins (a-CD and b-CD) are studied in aqueous as well as in solid state. The inclusion complexes are characterized by UV–visible, fluorescence, time correlated single photon counting, FTIR, DSC, PXRD and 1H NMR techniques. The self assembled SDA/CD and SFM/CD inclusion complexes form different types of nano and microstructures. The self assembled nanoparticle morphologies are studied using SEM and TEM techniques. SDA/a-CD complex is formed hierarchal morphology, SDA/b-CD and SFM/b-CD complexes form the nanosheet self assembly. However, SFM/a-CD complex forms nanoporous sheet self assembly. van der Waals, hydrophobic and hydrogen bonding interaction play a vital role in the self assembling process. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Cyclodextrins are a class of cyclic oligosaccharides with six to eight D-glucose units linked by a-1,4-glucose bonds. The shape of the CDs is a more symmetrical form resemble with a truncated cone. The wide opening is composed of secondary hydroxyl and narrow openings composed of primary hydroxyl groups. CDs has ability to incorporate a wide range of inorganic and organic guest ⇑ Corresponding author. Tel.: +91 94866 28800; fax: +91 4144 238080. E-mail address: [email protected] (N. Rajendiran). http://dx.doi.org/10.1016/j.saa.2014.03.028 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
molecules in their hydrophobic cavity mainly via hydrophobic and van der Waals interactions [1]. Moreover, it has been found that the interaction of appropriate shape and size guest molecule with CD can lead to assemblies such as rotaxanes [2], polyrotaxanes [3], and tubes [4]. In the past decade more efforts has been devoted to develop the fabrication of supramolecular nano and microstructures of various morphologies. These supramolecular nano and microstructures has their unique applications in the field of morphological dependent optical, electronic, magnetic and catalytic properties [5–9]. With this regard supramolecular materials such as cyclodextrin (CDs)
158
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
to meet the requirements of the well defined, regular and directional nano or microarchitecture [10]. CDs materials can be tailored through self assembly and self organized by the noncovalent interactions. Formation of guest induced CD self assembly has been the topic of current interest hence many researchers working in the applied field of chemical research. Jaffer et al. [11] reported intramolecular charge transfer probe induced formation of a-CD nanotubular suprastructures. Das et al. [12] studied the probe induced self aggregation of c-CD to nanotubular structure. Mandal et al. [13] study the c-CD host–guest complex and nanotube aggregate by fluorescence correlation spectroscopy. Wu et al. [14] observed micrometer rod like structure formed through secondary self assembly of the CD. The objective of the present work was to study the self assembly behavior of sulfadiazine (SDA) and sulfisomidine (SFM) drugs (Fig. 1) with a-CD and b-CD. The absorption and fluorescence characteristics of both SDA and SFM drugs with different solvents, pH and b-CD were already reported [15,16]. In our previous study we investigated inclusion complexation of some sulfonamide derivatives with b-CD. In the present work, we prepared solid inclusion complexes of the above two drugs with a-CD and b-CD and it was characterized by UV–visible, fluorescence, life time, FTIR, DSC, PXRD, 1H NMR, SEM and TEM and techniques. Experimental Materials SDA, SFM, a-CD and b-CD were purchased from Sigma–Aldrich chemical company and used without further purification. Preparation of nanomaterials A methanol solution of SDA or SFM (1 mmol, 10 ml) was added drop wise to an aqueous solution of CD (1 mmol, 40 ml). The above solution was stirred at 50 °C for 12 h. After the solution had been cooled to room temperature, the precipitate (white powder) was collected by filtration. The crude product was dissolved in hot water to make a saturated solution. After removal of the insoluble substances by filtration, a small amount of water was added to the filtrate. The resultant solution was kept at room temperature for several days, and the white powder was collected for solid analysis. Preparation of CD Solution Triply distilled water was used for the preparation of aqueous solutions. The concentration of stock solution of the drug was 2 10 3 M. 0.2 ml of the drug stock solution was transferred into 10 ml volumetric flasks. To this, varying concentration of CD
(a)
(b)
Fig. 1. Chemical structures of (a) SDA and (b) SFM.
solution (1 10 3 to 1 10 2 M) was added. The mixed solution was diluted to 10 ml with triply distilled water and shaken thoroughly. The final concentration of SDA and SFM in all the flasks was 4 10 5 M. All spectral measurements were performed at a solute concentration of 4 10 5 M. The experiments were carried out at room temperature. Instruments Scanning electron microscopy (SEM) photographs were collected on a JEOL JSM 5610LV instrument. The morphology of SDA or SFM encapsulated CDs inclusion complexes was investigated by transmission electron microscopy (TEM) using a TECNAI G2 microscope with accelerating voltage 200 kV. Carbon coated copper TEM grid (200 mesh) was used for the TEM analysis. FT-IR spectra of the SDA, SFM, CDs and the inclusion complexes were recorded between the wave number of 4000 cm 1 and 400 cm 1 on Nicolet Avatar 360 FT-IR spectrometer by using KBr pellets. One-dimensional 1H NMR spectra for SDA, SFM and its inclusion complexes were recorded on a Bruker AVANCE 400 MHz spectrometer (Germany) using DMSO-d6 (99.98%) as a solvent. The differential scanning calorimeter (DSC) was recorded using Mettler Toledo DSC1 fitted with STRe software (Mettler Toledo, Switzerland), temperature scanning range was from 25 to 220 °C with a heating rate of 10 °C/min. Powder X-ray diffraction (PXRD) spectra was recorded with a BRUKER D8 advance diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) and the pattern were measured in the 2h angle range between 5° and 80° with a scan rate 5°/min. Absorption spectral measurements were carried out with a Shimadzu (1601 model) UV–visible spectrophotometer and steady-state fluorescence measurements were made by using a Shimadzu spectrofluorimeter (RF-5301 model). The fluorescence lifetime measurements were performed using a picosecond laser and single photon counting setup from Jobin–Vyon IBH (Madras University, Chennai). Results and discussion Surface morphology The morphological changes of the sulfonamide drugs, CDs and inclusion complexes were observed by SEM (Fig. S1). These pictures clearly elucidated the difference between sulfonamides and their inclusion complexes. The SEM images of SDA and SFM are present in different forms from their inclusion complexes. The different morphological structures of isolated sulfa drugs and their inclusion complex were supporting the formation of inclusion complex nanomaterials. TEM was implying the morphology of the inclusion complex of SDA and SFM with CDs (Fig. S2). The TEM images of SDA/a-CD complex shown (Fig. S2a and b), hierarchal agglomerated structure with diameter of 750–1450 nm. SDA/b-CD complex forms a self assembled monolayer with length about 548 nm and diameter about 324 nm. These particles show a strong agreement between the center and margin, which is a distinctive typical nanosheet structure (Fig. S2c and d). It is obvious that the self assembly of SDA is the key for the typical hierarchal or sheet like agglomerates. SDA/b-CD inclusion nanomaterials are fixed in the head-to-head arrangement; i.e., monolayer or 1D sheet like agglomerate structure. But in SDA/a-CD, the guest is formed intermolecular hydrogen bonding (OH H) with a-CD; i.e., hierarchal shaped structure (Fig. 2). CDs having two types of hydroxyl groups on the end of the cavities, one is a primary hydroxyl group (tail) and another one is a secondary hydroxyl group (head). Hence, there is a possibility of three types of arrangement modes which CDs
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
(a)
(d)
159
(b)
(c)
Fig. 2. Proposed mechanism for the formation of 1D nanosheet: (a) inclusion complexes of SDA/b-CD, (b and c) randomly oriented pseudopolyrotaxanes of SDA/b-CD inclusion complexes formed by hydrogen bonding, (d) a molecular layer level (1D nanosheet) aggregation of pseudopolyrotaxanes of SDA/b-CD inclusion complexes.
can have interacted with each others, namely head-to-head, tailto-tail and head-to-tail [17,18]. From the above argument nanohierarchal agglomerate and 1D sheet architecture may be related to the weak supramolecular interaction, van der Waals force, hydrogen bond between neighboring complex and weaker assembling between the SDA with CDs. The formation of nanosheet through self assembling process was already reported [19,20]. Chandrasekhar and Chandrasekar [19] studied and confirmed the reversible shape-shifting of organic nanostructures and Dairong Chen and his co-workers was also reported similar type of results [20]. Dairong Chen and his co-workers fabricated mesoporous silica microtubes through the self assembly behavior of b-CD and Triton X-100 micelles. Besides, they reported that the intermolecular hydrogen bonding playing a crucial role in the supramolecular self assembling process. In the present case, we also observed intermolecular hydrogen bonding is the dominant driving force of the self assembling process. The proposed mechanism is shown in Fig. 2. In the first stage, the one dimensional individual SDA/b-CD complexes are changed to pseudopolyrotaxane like structure (Fig. 2b). Further, many of these pseudopolyrotaxane aggregate in the one molecular axis to form a single or a 1D molecular level layer (Fig. 2d). The nanoporous like structures are observed in the visible contrast between the porous and SFM/a-CD complex (Fig. S2e and f). These types of hallow porous sheet like materials were reported for different kinds of complexes [21–23]. SFM/b-CD inclusion complexes were self assembled to form a 1D sheet structure but different shape than that of SDA/b-CD complexes. Therefore, the same line of the arguments to be taken for the self assembling process of the SFM/b-CD inclusion complex. The nanoporous like structure formation of SFM/a-CD complex is ascribed to difference of relative formation rates of various crystalline phases. SFM/a-CD inclusion complex act as a building block and it has unique structural
features for the porous hierarchical supramolecular self assembly. The SFM/a-CD inclusion complexes have the essential shape of nanostructures (Fig. S2e and f) but they are not absolutely indistinguishable since the template has some discrepancy. Several SFM/ a-CD complexes are self assembled with various template effects, therefore nanoporous architecture shape will also have some dissimilar with unequal density (Fig. S2e and f). FTIR spectral analysis Fig. S3 depicts the FTIR spectra of free SDA, SFM and the inclusion complex nanomaterials. Amino group NAH stretching frequency appeared at 3497 cm 1 for SDA and 3466 cm 1 for SFM were becoming broad in the SDA/CD and SFM/CD inclusion complexes. The broadening of amino group NAH stretching band in inclusion complexes was due to the overlapping of CDs hydroxyl group stretching vibrations. The CAH stretching frequency appeared at 3062 cm 1 for SDA and 3069 cm 1 for SFM were shifted to lower frequency in the respective inclusion complexes. S@O stretching of SDA appeared at 1452 cm 1 is moved to 1442 cm 1 and 1440 cm 1 in SDA/a-CD and SDA/b-CD complex respectively. The S@O stretching frequency of SFM appeared at 1438 cm 1 is shifted to 1432 cm 1 and 1436 cm 1 in the SFM/a-CD and SFM/ b-CD complexes respectively. The NH2 deformation vibration peak intensity of SDA and SFM appeared at 1472 cm 1 and 1488 cm 1 respectively, were decreases in the SDA/CD and SFM/CD inclusion complexes. The SO2 deformation vibration of SDA appeared in the region 678 cm 1 was moved to higher frequencies in the SDA/a-CD and SDA/b-CD complexes. The aromatic CH out plane bending vibration of SFM appeared at 826 cm 1 was shifted to lower frequencies in the inclusion complexes. Further, some of frequencies of the SDA and SFM molecules in the region 1500–2000 cm 1 were lost in the inclusion complexes due to space
160
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
restriction of the CDs cavities. The above results indicate SDA and SFM molecules are included in the CD cavities and forms inclusion complex nanomaterials.
These observations indicate the formation of inclusion complex nanomaterials. X-ray diffraction analysis
Differential scanning calorimetry DSC has been shown to be a very powerful analytical tool in the characterization of solid-state interactions between the drugs and CDs. The DSC curves for isolated drugs and all the inclusion complex nanomaterials were reported in Fig. 3. SDA showed a typical behavior of anhydrous crystalline drug with a well defined melting peak at 238.6 °C. Due to loss of water, b-CD exhibited a very broad endothermal phenomenon between 128.6 °C (Fig. 3b). The endothermic peak which corresponds to the melting point of the SDA was not observed SDA/a-CD and SDA/b-CD indicating that an inclusion complex nanomaterial was formed. SDA/a-CD inclusion complex (Fig. 3d) show two endothermic peaks at 91.2 and 150.6 °C, the first one corresponds to loss of water from the sample and the second one is due to melting point of the complex nanomaterials. The SDA/b-CD complex (Fig. 3e) showed a broad endothermal peak at 112.5 °C, which is due to loss of water from the complex nanomaterials. SFM thermal curve (Fig. 3f) is typical crystalline anhydrous substances and is characterized by a sharp endothermic effect (at 227.9 °C), assigned to its melting point. The thermogram of the SFM/CD complexes (Fig. 3g and h) shows two broad endothermic effects due to the CD dehydration process. SFM melting peak disappeared in the corresponding inclusion complexes, which may be explained by weak interaction between the SFM and CD.
PXRD is a useful method for the detection of inclusion complexation in powder or microcrystalline states. Diffraction patterns of the complex should be clearly distinct from that of the superimposition of each component if a real inclusion complex nanomaterial has been formed. PXRD pattern of pure SDA and SFM drugs presented several diffraction peaks the indicating crystalline nature of the drug (Fig. 4). Both CDs has also exhibited a typical crystalline diffraction pattern. The diffractogram of SDA/a-CD (Fig. 4b) and SDA/b-CD (Fig. 4c) complexes differed from the corresponding SDA drug (Fig. 4a); i.e., in SDA, the intense diffraction peaks at 2h = 12.2°, 18.9°, 21.7° and 23.5° are dramatically affected in the inclusion complex nanomaterials. PXRD patterns of SFM, SFM/a-CD and SFM/b-CD are depicted in Fig. 4d–f. The diffractogram of SFM exhibited higher intense peaks at 2h = 9.8°, 15.2°, 18.9°, 19.7° and 24.6° due to the formation of inclusion complex. The intensity of these principal peaks of SFM decreased in the diffraction patterns of SFM/CD. This indicated that there was an interaction between the SFM and CD. Moreover, the diffraction pattern of the SDA/CD and SFM/CD complexes was more diffused as compared to pure components (SMA, SFM and CD). These observations were indicative of the transformation of SDA and SFM from crystalline to amorphous state, which might be the encapsulation of SDA and SFM into the CDs nanocavities. 1
H NMR spectral studies 1
(h) (g)
77.8 ºC 118.7 ºC
94.5 ºC
(f)
108.1 ºC
227.9 ºC
Exothermic (mW/mg)
(e)
(d)
112.5 ºC
91.2 ºC 150.6 ºC
(c)
238.6 ºC
(b)
(a)
H NMR spectroscopy provides an effective means of assessing the dynamic interaction site of the CD with that of the guest molecules. The resonance assignments of the protons of the CDs are well established [24–26] and consist of six types of protons. The chemical shift of b-CD protons reported are very close to those reported in this work. The chemical shift values are listed in Table 1 and the respective 1H NMR spectra are given in Figs. S4 and S5. As can be seen from Table 1, amino group protons (Ha) of SDA drug is down field shifted to +0.053 ppm in a-CD complex and +0.034 in b-CD complex. The aromatic protons of the SDA molecule (Hc, Hd, He and Hf) shift up field or down field as compared with the corresponding values those for free drugs. These results indicate that the above aromatic protons interact with CD cavity protons. Further, when compared to other protons, the higher chemical shift of Ha proton (SDA/a-CD = +0.053 ppm and SDA/b-CD = +0.034 ppm) suggests that amino proton of SDA molecule considerably interacted more with CDs. As can be seen from Table 1 and Figs. S4 and S5 chemical shifts for the inclusion complex were different from the isolated drug. In particular, the resonance of Ha (ANH) proton of SFM molecule indicates a down field shift in the inclusion (SFM/a-CD = +0.027 ppm and SFM/b-CD = +0.135 ppm). This higher chemical shift of Ha proton of SFM indicates that this proton may be hydrogen bonded with CD hydroxyl protons. In SFM/b-CD complex the amino proton Hc shifts up field (+0.042 ppm), which suggested that aromatic ring is shielded largely in the complex and it must penetrate deeply into the CDs nanocavities.
128.6 ºC
79.2 ºC
40
60
80
Absorbance and fluorescence spectral studies
109.1 ºC 137.5 ºC
100 120 140 160 180 200 220 240 260
Temperature (ºC) Fig. 3. DSC thermograms of (a) a-CD, (b) b-CD, (c) SDA, (d) SDA/a-CD, (e) SDA/b-CD, (f) SFM, (g) SFM/a-CD and (h) SFM/b-CD inclusion complex.
The inclusion complex nanomaterials formation of SDA and SFM with CD in aqueous solution was monitored by UV–visible and fluorescence spectroscopy. Fig. S6 shows the absorption spectra of SDA and SFM in the various concentrations of a-CD. The absorption and emission spectra of SDA and SFM in various
161
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
Fig. 4. PXRD patterns of (a) SDA, (b) SDA/a-CD, (c) SDA/b-CD, (d) SFM, (e) SFM/a-CD and (f) SFM/b-CD inclusion complex.
Table 1 H NMR chemical shift values for the SDA and SFM its inclusion complexes.
1
Protons
SDA (d)
SDA/a-CD (Dd)
SDA/b-CD (Dd)
SFM (d)
SFM/a-CD (Dd)
SFM/b-CD (Dd)
Ha Hb Hc Hd He Hf
11.197 7.617 6.994 5.963 8.461 6.547
+0.053 0.023 +0.015 +0.041 +0.005 0.005
+0.034 0.017 0.011 0.004 +0.003 +0.003
10.959 7.621 6.549 5.921 6.729 2.235
+0.027 +.008 0.017 +0.042 +0.059 0.004
+0.135 +0.047 +0.042 0.259 +0.006 +0.037
concentrations of b-CD were not provided, because it is already reported [15,16]. Upon the addition of b-CD, the absorption maxima of the SDA and SFM molecules are red shifted with gradual increase in the molar coefficient, whereas, in the case of a-CD absorbance increased at the same wavelength. The increase in the absorbance is due to the encapsulation of the drug molecules into the CDs nanocavities and it is attributed to the detergent action of CDs [27–32]. Fig. S7 shows the fluorescence spectra of SDA and SFM in aqueous solution as a function of a-CD concentrations. In aqueous medium, the intensity of the shorter wavelength (SW) is greater than longer wavelength (LW) intensity. However, an addition of CDs, both SW and LW intensities are equally increased. With an increase in the a-CD concentration, both the SW and LW emission intensity of the SDA and SFM drugs were gradually increased at the same emission wavelength. Moreover, both guest molecules show larger enhancement in b-CD solution than that of the a-CD. The reason for the enhancement of both SW and LW bands of the SDA and SFM are already explained in our earlier reports [15,16]. Both absorption and fluorescence spectra results reveal that both SDA and SFM molecules form stable inclusion complex nanomaterials in the aqueous solution. The fluorescence lifetime values of SDA and SFM in water, 0.01 M, a-CD and b-CD medium has been monitored. The relevant data are compiled in Table 2 and fluorescence decay curves are
shown in Fig. S8. We notice that two decay components for SDA and SFM drugs in aqueous medium, which arise from populations differing in the extent of hydrogen bonding. But in CD solution, SDA and SFM show three decay components. In SDA, compared to water (s = 2.83 ns), CDs solution shows high lifetime (SDA/a-CD = 2.86 ns and SDA/b-CD = 3.02 ns). However, SFM/a-CD and SFM/b-CD show relatively higher lifetime value than that of SDA in aqueous solution. The observed enhancement in lifetime indicates that SDA and SFM molecules experience less polar hydrophobic environments within the CD nanocavity resulting in the reduction of non-radiative decay process. This might be due to the variation in the microscopic environment experienced by these molecules in the presence of CD solution, which is Table 2 Fluorescence decay parameters of SDA and SFM in water and 0.01 M CD solution. Drugs
Medium
s1
s2
SDA
Water a-CD b-CD
0.29 1.14 0.55
3.28 4.58 3.83
Water
0.93 0.52 0.34
4.25 1.79 4.18
SFM
a-CD b-CD
Lifetime (ns)
Preexponential factor
s3
8.75 10.56
a1
a2
0.17 0.12 0.09
0.06 0.03 0.04
0.07 0.12 0.20
0.05 0.04 0.09
a3 2.83 2.86 3.02 0.007 0.01
3.47 3.05 4.93
162
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
expected to be quite different from the pure solvent. The results indicate that these molecules were encapsulated in the CDs nanocavities. Conclusions The supramolecular self assembly of the SDA/CD and SFM/CD inclusion complex nanomaterials are studied by using SEM and TEM techniques. The formation of inclusion complex nanomaterials was confirmed by UV–visible, fluorescence, life time, FTIR, DSC, PXRD and 1H NMR spectroscopy. The results indicate that the van der Waals, hydrophobic and hydrogen bonding interactions play a major role in the self assembling process of SDA/CD and SFM/CD nanomaterials. The SDA/a-CD complex self assembled to form the hierarchal structure and SFM/a-CD complex form a nanoporous sheet structure, whereas SDA/b-CD and SFM/b-CD complexes form a monolayer or 1D nanosheet structure. Acknowledgements This work was supported by the Council of Scientific Industrial Research [No. 01(2549)/12/EMR-II] and the University Grants Commission [F. No. 41-351/2012(SR)] New Delhi, India. One of the authors, G. Venkatesh is thankful to the University Grants Commission New Delhi, India for the award of BSR-SAP fellowship. The authors thank Dr. P. Ramamurthy, Director, National Centre for Ultrafast Processes, Madras University for allowing the fluorescence lifetime measurements for this work. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.03.028. References [1] G. Pistolis, I. Balomenou, J. Phys. Chem. B 110 (2006) 16428–16438. [2] R.S. Wylie, D.H. Macartney, J. Am. Chem. Soc. 114 (1992) 3136–3138. [3] T. Zhao, H.W. Beckham, Macromolecules 36 (2003) 9859–9865.
[4] D.T. Bong, T.D. Clark, J.R. Granja, M.R. Ghadiri, Angew. Chem., Int. Ed. 40 (2001) 988–1011. [5] M.A. El-Sayed, Acc. Chem. Res. 34 (2001) 257–264. [6] S. Iijima, Nature 354 (1991) 56–58. [7] H. Friedrich, P.E. de Jongh, A.J. Verkleij, K.P. de Jong, Chem. Rev. 109 (2009) 1613–1629. [8] Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, A. Yan, Adv. Mater. 15 (2003) 353–389. [9] B.B. Lakshmi, P.K. Dorhout, C.R. Martin, Chem. Mater. 9 (1997) 857–862. [10] T. Sun, H. Zhang, L. Komg, H. Qiao, Y. Li, F. Xin, A. Hao, Carbohydr. Res. 346 (2011) 285–293. [11] S.S. Jaffer, S.K. Saha, G. Eranna, A.K. Sharma, P. Purkayastha, J. Phys. Chem. C 112 (2008) 11199–11204. [12] P. Das, A. Mallick, D. Sarkar, N. Chattopadhyay, J. Phys. Chem. C 112 (2008) 9600–9603. [13] A.K. Mandal, D.K. Das, A.K. Das, S.S. Mojumdar, K. Bhattacharyya, J. Phys. Chem. B 115 (2011) 10456–10461. [14] A. Wu, X. Shen, Y. He, J. Colloid Interface Sci. 302 (2006) 87–94. [15] J. Premakumari, G. Allan Gnana Roy, A. Antony Muthu Prabhu, G. Venkatesh, V.K. Subramanian, N. Rajendiran, Phys. Chem. Liq. 49 (2011) 108–132. [16] A. Antony Muthu Prabhu, G. Venkatesh, N. Rajendiran, J. Sol. Chem. 39 (2010) 1061–1086. [17] Y. Lu, G.-S. Chen, Y. Chen, N. Zhang, J. Chen, Y.-L. Zhao, Nano Lett. 6 (2006) 2196–2200. [18] J.W. Chung, T.J. Kang, S-Y. Kwak, Langmuir 23 (2007) 12366–12370. [19] N. Chandrasekhar, R. Chandrasekar, Angew. Chem., Int. Ed. 51 (2012) 3556– 3561. [20] D. Chen, Q. Lu, X. Jiao, Chem. Mater. 17 (2005) 4168–4173. [21] R.C. Sabapathy, S. Battacharyya, W.E. Cleland, C.L. Hussey, Langmuir 14 (1998) 3797–3807. [22] Y. Liu, C.F. Ke, H.Y. Zhang, J. Cui, F. Ding, J. Am. Chem. Soc. 130 (2008) 600–605. [23] R.S. Forgan, R.A. Smaldone, J.J. Gassensmith, H. Furukawa, D.B. Cordes, Q. Li, C.E. Wilmer, Y.Y. Botros, R.Q. Snurr, A.M.Z. Slawin, J.F. Stoddart, J. Am. Chem. Soc. 134 (2012) 406–417. [24] H.J. Schneider, F. Hacket, V. Rudiger, H. Ikeda, Chem. Rev. 98 (1998) 1755– 1786. [25] A. Abdul-Shafi, S. Al-Shihry, Spectrochim. Acta, Part A 66 (2007) 732–738. [26] J. Premakumari, G. Allan Gnana Roy, A. Antony Muthu Prabhu, G. Venkatesh, V.K. Subramanian, N. Rajendiran, J. Sol. Chem. 40 (2011) 327–347. [27] T. Sivasankar, A. Antony Muthu Prabhu, M. Karthick, N. Rajendiran, J. Mol. Struct. 1028 (2012) 57–67. [28] A. Antony Muthu Prabhu, V.K. Subramanian, N. Rajendiran, Spectrochim. Acta, Part A 96 (2012) 95–107. [29] S. Siva, G. Venkatesh, A. Antony Muthu Prabhu, R.K. Sankaranarayanan, N. Rajendiran, Phys. Chem. Liq. 50 (2012) 434–452. [30] A. Antony Muthu Prabhu, R.K. Sankaranarayanan, G. Venkatesh, N. Rajendiran, J. Phys. Chem. B 116 (2012) 9061–9074. [31] G. Venkatesh, A. Antony Muthu Prabhu, N. Rajendiran, J. Fluorescence 21 (2011) 1485–1497. [32] A. Antony Muthu Prabhu, N. Rajendiran, J. Fluorescence 22 (2012) 1461–1474.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Supramolecular aggregates formed by sulfadiazine and sulfisomidine inclusion complexes with a- and b-cyclodextrins N. Rajendiran ⇑, G. Venkatesh, J. Saravanan Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
SDA/a-CD complex self assembled to
formed hierarchal morphology. SDA/b-CD and SFM/b-CD complexes
self assembled to form the nanosheet. SFM/a-CD complex self assembled to
form nanoporous sheet. van der Waals, hydrophobic and
hydrogen bonding interactions play a vital role in the self assembling process.
a r t i c l e
i n f o
Article history: Received 1 December 2013 Received in revised form 5 March 2014 Accepted 18 March 2014 Available online 28 March 2014 Keywords: Sulfa drugs Cyclodextrins Inclusion complex Self assembly Nanosheet Nanomaterial
a b s t r a c t Sulfadiazine (SDA) and sulfisomidine (SFM) inclusion complexes with two cyclodextrins (a-CD and b-CD) are studied in aqueous as well as in solid state. The inclusion complexes are characterized by UV–visible, fluorescence, time correlated single photon counting, FTIR, DSC, PXRD and 1H NMR techniques. The self assembled SDA/CD and SFM/CD inclusion complexes form different types of nano and microstructures. The self assembled nanoparticle morphologies are studied using SEM and TEM techniques. SDA/a-CD complex is formed hierarchal morphology, SDA/b-CD and SFM/b-CD complexes form the nanosheet self assembly. However, SFM/a-CD complex forms nanoporous sheet self assembly. van der Waals, hydrophobic and hydrogen bonding interaction play a vital role in the self assembling process. Ó 2014 Elsevier B.V. All rights reserved.
Introduction Cyclodextrins are a class of cyclic oligosaccharides with six to eight D-glucose units linked by a-1,4-glucose bonds. The shape of the CDs is a more symmetrical form resemble with a truncated cone. The wide opening is composed of secondary hydroxyl and narrow openings composed of primary hydroxyl groups. CDs has ability to incorporate a wide range of inorganic and organic guest ⇑ Corresponding author. Tel.: +91 94866 28800; fax: +91 4144 238080. E-mail address: [email protected] (N. Rajendiran). http://dx.doi.org/10.1016/j.saa.2014.03.028 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
molecules in their hydrophobic cavity mainly via hydrophobic and van der Waals interactions [1]. Moreover, it has been found that the interaction of appropriate shape and size guest molecule with CD can lead to assemblies such as rotaxanes [2], polyrotaxanes [3], and tubes [4]. In the past decade more efforts has been devoted to develop the fabrication of supramolecular nano and microstructures of various morphologies. These supramolecular nano and microstructures has their unique applications in the field of morphological dependent optical, electronic, magnetic and catalytic properties [5–9]. With this regard supramolecular materials such as cyclodextrin (CDs)
158
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
to meet the requirements of the well defined, regular and directional nano or microarchitecture [10]. CDs materials can be tailored through self assembly and self organized by the noncovalent interactions. Formation of guest induced CD self assembly has been the topic of current interest hence many researchers working in the applied field of chemical research. Jaffer et al. [11] reported intramolecular charge transfer probe induced formation of a-CD nanotubular suprastructures. Das et al. [12] studied the probe induced self aggregation of c-CD to nanotubular structure. Mandal et al. [13] study the c-CD host–guest complex and nanotube aggregate by fluorescence correlation spectroscopy. Wu et al. [14] observed micrometer rod like structure formed through secondary self assembly of the CD. The objective of the present work was to study the self assembly behavior of sulfadiazine (SDA) and sulfisomidine (SFM) drugs (Fig. 1) with a-CD and b-CD. The absorption and fluorescence characteristics of both SDA and SFM drugs with different solvents, pH and b-CD were already reported [15,16]. In our previous study we investigated inclusion complexation of some sulfonamide derivatives with b-CD. In the present work, we prepared solid inclusion complexes of the above two drugs with a-CD and b-CD and it was characterized by UV–visible, fluorescence, life time, FTIR, DSC, PXRD, 1H NMR, SEM and TEM and techniques. Experimental Materials SDA, SFM, a-CD and b-CD were purchased from Sigma–Aldrich chemical company and used without further purification. Preparation of nanomaterials A methanol solution of SDA or SFM (1 mmol, 10 ml) was added drop wise to an aqueous solution of CD (1 mmol, 40 ml). The above solution was stirred at 50 °C for 12 h. After the solution had been cooled to room temperature, the precipitate (white powder) was collected by filtration. The crude product was dissolved in hot water to make a saturated solution. After removal of the insoluble substances by filtration, a small amount of water was added to the filtrate. The resultant solution was kept at room temperature for several days, and the white powder was collected for solid analysis. Preparation of CD Solution Triply distilled water was used for the preparation of aqueous solutions. The concentration of stock solution of the drug was 2 10 3 M. 0.2 ml of the drug stock solution was transferred into 10 ml volumetric flasks. To this, varying concentration of CD
(a)
(b)
Fig. 1. Chemical structures of (a) SDA and (b) SFM.
solution (1 10 3 to 1 10 2 M) was added. The mixed solution was diluted to 10 ml with triply distilled water and shaken thoroughly. The final concentration of SDA and SFM in all the flasks was 4 10 5 M. All spectral measurements were performed at a solute concentration of 4 10 5 M. The experiments were carried out at room temperature. Instruments Scanning electron microscopy (SEM) photographs were collected on a JEOL JSM 5610LV instrument. The morphology of SDA or SFM encapsulated CDs inclusion complexes was investigated by transmission electron microscopy (TEM) using a TECNAI G2 microscope with accelerating voltage 200 kV. Carbon coated copper TEM grid (200 mesh) was used for the TEM analysis. FT-IR spectra of the SDA, SFM, CDs and the inclusion complexes were recorded between the wave number of 4000 cm 1 and 400 cm 1 on Nicolet Avatar 360 FT-IR spectrometer by using KBr pellets. One-dimensional 1H NMR spectra for SDA, SFM and its inclusion complexes were recorded on a Bruker AVANCE 400 MHz spectrometer (Germany) using DMSO-d6 (99.98%) as a solvent. The differential scanning calorimeter (DSC) was recorded using Mettler Toledo DSC1 fitted with STRe software (Mettler Toledo, Switzerland), temperature scanning range was from 25 to 220 °C with a heating rate of 10 °C/min. Powder X-ray diffraction (PXRD) spectra was recorded with a BRUKER D8 advance diffractometer (Bruker AXS GmbH, Karlsruhe, Germany) and the pattern were measured in the 2h angle range between 5° and 80° with a scan rate 5°/min. Absorption spectral measurements were carried out with a Shimadzu (1601 model) UV–visible spectrophotometer and steady-state fluorescence measurements were made by using a Shimadzu spectrofluorimeter (RF-5301 model). The fluorescence lifetime measurements were performed using a picosecond laser and single photon counting setup from Jobin–Vyon IBH (Madras University, Chennai). Results and discussion Surface morphology The morphological changes of the sulfonamide drugs, CDs and inclusion complexes were observed by SEM (Fig. S1). These pictures clearly elucidated the difference between sulfonamides and their inclusion complexes. The SEM images of SDA and SFM are present in different forms from their inclusion complexes. The different morphological structures of isolated sulfa drugs and their inclusion complex were supporting the formation of inclusion complex nanomaterials. TEM was implying the morphology of the inclusion complex of SDA and SFM with CDs (Fig. S2). The TEM images of SDA/a-CD complex shown (Fig. S2a and b), hierarchal agglomerated structure with diameter of 750–1450 nm. SDA/b-CD complex forms a self assembled monolayer with length about 548 nm and diameter about 324 nm. These particles show a strong agreement between the center and margin, which is a distinctive typical nanosheet structure (Fig. S2c and d). It is obvious that the self assembly of SDA is the key for the typical hierarchal or sheet like agglomerates. SDA/b-CD inclusion nanomaterials are fixed in the head-to-head arrangement; i.e., monolayer or 1D sheet like agglomerate structure. But in SDA/a-CD, the guest is formed intermolecular hydrogen bonding (OH H) with a-CD; i.e., hierarchal shaped structure (Fig. 2). CDs having two types of hydroxyl groups on the end of the cavities, one is a primary hydroxyl group (tail) and another one is a secondary hydroxyl group (head). Hence, there is a possibility of three types of arrangement modes which CDs
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
(a)
(d)
159
(b)
(c)
Fig. 2. Proposed mechanism for the formation of 1D nanosheet: (a) inclusion complexes of SDA/b-CD, (b and c) randomly oriented pseudopolyrotaxanes of SDA/b-CD inclusion complexes formed by hydrogen bonding, (d) a molecular layer level (1D nanosheet) aggregation of pseudopolyrotaxanes of SDA/b-CD inclusion complexes.
can have interacted with each others, namely head-to-head, tailto-tail and head-to-tail [17,18]. From the above argument nanohierarchal agglomerate and 1D sheet architecture may be related to the weak supramolecular interaction, van der Waals force, hydrogen bond between neighboring complex and weaker assembling between the SDA with CDs. The formation of nanosheet through self assembling process was already reported [19,20]. Chandrasekhar and Chandrasekar [19] studied and confirmed the reversible shape-shifting of organic nanostructures and Dairong Chen and his co-workers was also reported similar type of results [20]. Dairong Chen and his co-workers fabricated mesoporous silica microtubes through the self assembly behavior of b-CD and Triton X-100 micelles. Besides, they reported that the intermolecular hydrogen bonding playing a crucial role in the supramolecular self assembling process. In the present case, we also observed intermolecular hydrogen bonding is the dominant driving force of the self assembling process. The proposed mechanism is shown in Fig. 2. In the first stage, the one dimensional individual SDA/b-CD complexes are changed to pseudopolyrotaxane like structure (Fig. 2b). Further, many of these pseudopolyrotaxane aggregate in the one molecular axis to form a single or a 1D molecular level layer (Fig. 2d). The nanoporous like structures are observed in the visible contrast between the porous and SFM/a-CD complex (Fig. S2e and f). These types of hallow porous sheet like materials were reported for different kinds of complexes [21–23]. SFM/b-CD inclusion complexes were self assembled to form a 1D sheet structure but different shape than that of SDA/b-CD complexes. Therefore, the same line of the arguments to be taken for the self assembling process of the SFM/b-CD inclusion complex. The nanoporous like structure formation of SFM/a-CD complex is ascribed to difference of relative formation rates of various crystalline phases. SFM/a-CD inclusion complex act as a building block and it has unique structural
features for the porous hierarchical supramolecular self assembly. The SFM/a-CD inclusion complexes have the essential shape of nanostructures (Fig. S2e and f) but they are not absolutely indistinguishable since the template has some discrepancy. Several SFM/ a-CD complexes are self assembled with various template effects, therefore nanoporous architecture shape will also have some dissimilar with unequal density (Fig. S2e and f). FTIR spectral analysis Fig. S3 depicts the FTIR spectra of free SDA, SFM and the inclusion complex nanomaterials. Amino group NAH stretching frequency appeared at 3497 cm 1 for SDA and 3466 cm 1 for SFM were becoming broad in the SDA/CD and SFM/CD inclusion complexes. The broadening of amino group NAH stretching band in inclusion complexes was due to the overlapping of CDs hydroxyl group stretching vibrations. The CAH stretching frequency appeared at 3062 cm 1 for SDA and 3069 cm 1 for SFM were shifted to lower frequency in the respective inclusion complexes. S@O stretching of SDA appeared at 1452 cm 1 is moved to 1442 cm 1 and 1440 cm 1 in SDA/a-CD and SDA/b-CD complex respectively. The S@O stretching frequency of SFM appeared at 1438 cm 1 is shifted to 1432 cm 1 and 1436 cm 1 in the SFM/a-CD and SFM/ b-CD complexes respectively. The NH2 deformation vibration peak intensity of SDA and SFM appeared at 1472 cm 1 and 1488 cm 1 respectively, were decreases in the SDA/CD and SFM/CD inclusion complexes. The SO2 deformation vibration of SDA appeared in the region 678 cm 1 was moved to higher frequencies in the SDA/a-CD and SDA/b-CD complexes. The aromatic CH out plane bending vibration of SFM appeared at 826 cm 1 was shifted to lower frequencies in the inclusion complexes. Further, some of frequencies of the SDA and SFM molecules in the region 1500–2000 cm 1 were lost in the inclusion complexes due to space
160
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
restriction of the CDs cavities. The above results indicate SDA and SFM molecules are included in the CD cavities and forms inclusion complex nanomaterials.
These observations indicate the formation of inclusion complex nanomaterials. X-ray diffraction analysis
Differential scanning calorimetry DSC has been shown to be a very powerful analytical tool in the characterization of solid-state interactions between the drugs and CDs. The DSC curves for isolated drugs and all the inclusion complex nanomaterials were reported in Fig. 3. SDA showed a typical behavior of anhydrous crystalline drug with a well defined melting peak at 238.6 °C. Due to loss of water, b-CD exhibited a very broad endothermal phenomenon between 128.6 °C (Fig. 3b). The endothermic peak which corresponds to the melting point of the SDA was not observed SDA/a-CD and SDA/b-CD indicating that an inclusion complex nanomaterial was formed. SDA/a-CD inclusion complex (Fig. 3d) show two endothermic peaks at 91.2 and 150.6 °C, the first one corresponds to loss of water from the sample and the second one is due to melting point of the complex nanomaterials. The SDA/b-CD complex (Fig. 3e) showed a broad endothermal peak at 112.5 °C, which is due to loss of water from the complex nanomaterials. SFM thermal curve (Fig. 3f) is typical crystalline anhydrous substances and is characterized by a sharp endothermic effect (at 227.9 °C), assigned to its melting point. The thermogram of the SFM/CD complexes (Fig. 3g and h) shows two broad endothermic effects due to the CD dehydration process. SFM melting peak disappeared in the corresponding inclusion complexes, which may be explained by weak interaction between the SFM and CD.
PXRD is a useful method for the detection of inclusion complexation in powder or microcrystalline states. Diffraction patterns of the complex should be clearly distinct from that of the superimposition of each component if a real inclusion complex nanomaterial has been formed. PXRD pattern of pure SDA and SFM drugs presented several diffraction peaks the indicating crystalline nature of the drug (Fig. 4). Both CDs has also exhibited a typical crystalline diffraction pattern. The diffractogram of SDA/a-CD (Fig. 4b) and SDA/b-CD (Fig. 4c) complexes differed from the corresponding SDA drug (Fig. 4a); i.e., in SDA, the intense diffraction peaks at 2h = 12.2°, 18.9°, 21.7° and 23.5° are dramatically affected in the inclusion complex nanomaterials. PXRD patterns of SFM, SFM/a-CD and SFM/b-CD are depicted in Fig. 4d–f. The diffractogram of SFM exhibited higher intense peaks at 2h = 9.8°, 15.2°, 18.9°, 19.7° and 24.6° due to the formation of inclusion complex. The intensity of these principal peaks of SFM decreased in the diffraction patterns of SFM/CD. This indicated that there was an interaction between the SFM and CD. Moreover, the diffraction pattern of the SDA/CD and SFM/CD complexes was more diffused as compared to pure components (SMA, SFM and CD). These observations were indicative of the transformation of SDA and SFM from crystalline to amorphous state, which might be the encapsulation of SDA and SFM into the CDs nanocavities. 1
H NMR spectral studies 1
(h) (g)
77.8 ºC 118.7 ºC
94.5 ºC
(f)
108.1 ºC
227.9 ºC
Exothermic (mW/mg)
(e)
(d)
112.5 ºC
91.2 ºC 150.6 ºC
(c)
238.6 ºC
(b)
(a)
H NMR spectroscopy provides an effective means of assessing the dynamic interaction site of the CD with that of the guest molecules. The resonance assignments of the protons of the CDs are well established [24–26] and consist of six types of protons. The chemical shift of b-CD protons reported are very close to those reported in this work. The chemical shift values are listed in Table 1 and the respective 1H NMR spectra are given in Figs. S4 and S5. As can be seen from Table 1, amino group protons (Ha) of SDA drug is down field shifted to +0.053 ppm in a-CD complex and +0.034 in b-CD complex. The aromatic protons of the SDA molecule (Hc, Hd, He and Hf) shift up field or down field as compared with the corresponding values those for free drugs. These results indicate that the above aromatic protons interact with CD cavity protons. Further, when compared to other protons, the higher chemical shift of Ha proton (SDA/a-CD = +0.053 ppm and SDA/b-CD = +0.034 ppm) suggests that amino proton of SDA molecule considerably interacted more with CDs. As can be seen from Table 1 and Figs. S4 and S5 chemical shifts for the inclusion complex were different from the isolated drug. In particular, the resonance of Ha (ANH) proton of SFM molecule indicates a down field shift in the inclusion (SFM/a-CD = +0.027 ppm and SFM/b-CD = +0.135 ppm). This higher chemical shift of Ha proton of SFM indicates that this proton may be hydrogen bonded with CD hydroxyl protons. In SFM/b-CD complex the amino proton Hc shifts up field (+0.042 ppm), which suggested that aromatic ring is shielded largely in the complex and it must penetrate deeply into the CDs nanocavities.
128.6 ºC
79.2 ºC
40
60
80
Absorbance and fluorescence spectral studies
109.1 ºC 137.5 ºC
100 120 140 160 180 200 220 240 260
Temperature (ºC) Fig. 3. DSC thermograms of (a) a-CD, (b) b-CD, (c) SDA, (d) SDA/a-CD, (e) SDA/b-CD, (f) SFM, (g) SFM/a-CD and (h) SFM/b-CD inclusion complex.
The inclusion complex nanomaterials formation of SDA and SFM with CD in aqueous solution was monitored by UV–visible and fluorescence spectroscopy. Fig. S6 shows the absorption spectra of SDA and SFM in the various concentrations of a-CD. The absorption and emission spectra of SDA and SFM in various
161
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
Fig. 4. PXRD patterns of (a) SDA, (b) SDA/a-CD, (c) SDA/b-CD, (d) SFM, (e) SFM/a-CD and (f) SFM/b-CD inclusion complex.
Table 1 H NMR chemical shift values for the SDA and SFM its inclusion complexes.
1
Protons
SDA (d)
SDA/a-CD (Dd)
SDA/b-CD (Dd)
SFM (d)
SFM/a-CD (Dd)
SFM/b-CD (Dd)
Ha Hb Hc Hd He Hf
11.197 7.617 6.994 5.963 8.461 6.547
+0.053 0.023 +0.015 +0.041 +0.005 0.005
+0.034 0.017 0.011 0.004 +0.003 +0.003
10.959 7.621 6.549 5.921 6.729 2.235
+0.027 +.008 0.017 +0.042 +0.059 0.004
+0.135 +0.047 +0.042 0.259 +0.006 +0.037
concentrations of b-CD were not provided, because it is already reported [15,16]. Upon the addition of b-CD, the absorption maxima of the SDA and SFM molecules are red shifted with gradual increase in the molar coefficient, whereas, in the case of a-CD absorbance increased at the same wavelength. The increase in the absorbance is due to the encapsulation of the drug molecules into the CDs nanocavities and it is attributed to the detergent action of CDs [27–32]. Fig. S7 shows the fluorescence spectra of SDA and SFM in aqueous solution as a function of a-CD concentrations. In aqueous medium, the intensity of the shorter wavelength (SW) is greater than longer wavelength (LW) intensity. However, an addition of CDs, both SW and LW intensities are equally increased. With an increase in the a-CD concentration, both the SW and LW emission intensity of the SDA and SFM drugs were gradually increased at the same emission wavelength. Moreover, both guest molecules show larger enhancement in b-CD solution than that of the a-CD. The reason for the enhancement of both SW and LW bands of the SDA and SFM are already explained in our earlier reports [15,16]. Both absorption and fluorescence spectra results reveal that both SDA and SFM molecules form stable inclusion complex nanomaterials in the aqueous solution. The fluorescence lifetime values of SDA and SFM in water, 0.01 M, a-CD and b-CD medium has been monitored. The relevant data are compiled in Table 2 and fluorescence decay curves are
shown in Fig. S8. We notice that two decay components for SDA and SFM drugs in aqueous medium, which arise from populations differing in the extent of hydrogen bonding. But in CD solution, SDA and SFM show three decay components. In SDA, compared to water (s = 2.83 ns), CDs solution shows high lifetime (SDA/a-CD = 2.86 ns and SDA/b-CD = 3.02 ns). However, SFM/a-CD and SFM/b-CD show relatively higher lifetime value than that of SDA in aqueous solution. The observed enhancement in lifetime indicates that SDA and SFM molecules experience less polar hydrophobic environments within the CD nanocavity resulting in the reduction of non-radiative decay process. This might be due to the variation in the microscopic environment experienced by these molecules in the presence of CD solution, which is Table 2 Fluorescence decay parameters of SDA and SFM in water and 0.01 M CD solution. Drugs
Medium
s1
s2
SDA
Water a-CD b-CD
0.29 1.14 0.55
3.28 4.58 3.83
Water
0.93 0.52 0.34
4.25 1.79 4.18
SFM
a-CD b-CD
Lifetime (ns)
Preexponential factor
s3
8.75 10.56
a1
a2
0.17 0.12 0.09
0.06 0.03 0.04
0.07 0.12 0.20
0.05 0.04 0.09
a3 2.83 2.86 3.02 0.007 0.01
3.47 3.05 4.93
162
N. Rajendiran et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 129 (2014) 157–162
expected to be quite different from the pure solvent. The results indicate that these molecules were encapsulated in the CDs nanocavities. Conclusions The supramolecular self assembly of the SDA/CD and SFM/CD inclusion complex nanomaterials are studied by using SEM and TEM techniques. The formation of inclusion complex nanomaterials was confirmed by UV–visible, fluorescence, life time, FTIR, DSC, PXRD and 1H NMR spectroscopy. The results indicate that the van der Waals, hydrophobic and hydrogen bonding interactions play a major role in the self assembling process of SDA/CD and SFM/CD nanomaterials. The SDA/a-CD complex self assembled to form the hierarchal structure and SFM/a-CD complex form a nanoporous sheet structure, whereas SDA/b-CD and SFM/b-CD complexes form a monolayer or 1D nanosheet structure. Acknowledgements This work was supported by the Council of Scientific Industrial Research [No. 01(2549)/12/EMR-II] and the University Grants Commission [F. No. 41-351/2012(SR)] New Delhi, India. One of the authors, G. Venkatesh is thankful to the University Grants Commission New Delhi, India for the award of BSR-SAP fellowship. The authors thank Dr. P. Ramamurthy, Director, National Centre for Ultrafast Processes, Madras University for allowing the fluorescence lifetime measurements for this work. Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.saa.2014.03.028. References [1] G. Pistolis, I. Balomenou, J. Phys. Chem. B 110 (2006) 16428–16438. [2] R.S. Wylie, D.H. Macartney, J. Am. Chem. Soc. 114 (1992) 3136–3138. [3] T. Zhao, H.W. Beckham, Macromolecules 36 (2003) 9859–9865.
[4] D.T. Bong, T.D. Clark, J.R. Granja, M.R. Ghadiri, Angew. Chem., Int. Ed. 40 (2001) 988–1011. [5] M.A. El-Sayed, Acc. Chem. Res. 34 (2001) 257–264. [6] S. Iijima, Nature 354 (1991) 56–58. [7] H. Friedrich, P.E. de Jongh, A.J. Verkleij, K.P. de Jong, Chem. Rev. 109 (2009) 1613–1629. [8] Y. Xia, P. Yang, Y. Sun, Y. Wu, B. Mayers, B. Gates, Y. Yin, F. Kim, A. Yan, Adv. Mater. 15 (2003) 353–389. [9] B.B. Lakshmi, P.K. Dorhout, C.R. Martin, Chem. Mater. 9 (1997) 857–862. [10] T. Sun, H. Zhang, L. Komg, H. Qiao, Y. Li, F. Xin, A. Hao, Carbohydr. Res. 346 (2011) 285–293. [11] S.S. Jaffer, S.K. Saha, G. Eranna, A.K. Sharma, P. Purkayastha, J. Phys. Chem. C 112 (2008) 11199–11204. [12] P. Das, A. Mallick, D. Sarkar, N. Chattopadhyay, J. Phys. Chem. C 112 (2008) 9600–9603. [13] A.K. Mandal, D.K. Das, A.K. Das, S.S. Mojumdar, K. Bhattacharyya, J. Phys. Chem. B 115 (2011) 10456–10461. [14] A. Wu, X. Shen, Y. He, J. Colloid Interface Sci. 302 (2006) 87–94. [15] J. Premakumari, G. Allan Gnana Roy, A. Antony Muthu Prabhu, G. Venkatesh, V.K. Subramanian, N. Rajendiran, Phys. Chem. Liq. 49 (2011) 108–132. [16] A. Antony Muthu Prabhu, G. Venkatesh, N. Rajendiran, J. Sol. Chem. 39 (2010) 1061–1086. [17] Y. Lu, G.-S. Chen, Y. Chen, N. Zhang, J. Chen, Y.-L. Zhao, Nano Lett. 6 (2006) 2196–2200. [18] J.W. Chung, T.J. Kang, S-Y. Kwak, Langmuir 23 (2007) 12366–12370. [19] N. Chandrasekhar, R. Chandrasekar, Angew. Chem., Int. Ed. 51 (2012) 3556– 3561. [20] D. Chen, Q. Lu, X. Jiao, Chem. Mater. 17 (2005) 4168–4173. [21] R.C. Sabapathy, S. Battacharyya, W.E. Cleland, C.L. Hussey, Langmuir 14 (1998) 3797–3807. [22] Y. Liu, C.F. Ke, H.Y. Zhang, J. Cui, F. Ding, J. Am. Chem. Soc. 130 (2008) 600–605. [23] R.S. Forgan, R.A. Smaldone, J.J. Gassensmith, H. Furukawa, D.B. Cordes, Q. Li, C.E. Wilmer, Y.Y. Botros, R.Q. Snurr, A.M.Z. Slawin, J.F. Stoddart, J. Am. Chem. Soc. 134 (2012) 406–417. [24] H.J. Schneider, F. Hacket, V. Rudiger, H. Ikeda, Chem. Rev. 98 (1998) 1755– 1786. [25] A. Abdul-Shafi, S. Al-Shihry, Spectrochim. Acta, Part A 66 (2007) 732–738. [26] J. Premakumari, G. Allan Gnana Roy, A. Antony Muthu Prabhu, G. Venkatesh, V.K. Subramanian, N. Rajendiran, J. Sol. Chem. 40 (2011) 327–347. [27] T. Sivasankar, A. Antony Muthu Prabhu, M. Karthick, N. Rajendiran, J. Mol. Struct. 1028 (2012) 57–67. [28] A. Antony Muthu Prabhu, V.K. Subramanian, N. Rajendiran, Spectrochim. Acta, Part A 96 (2012) 95–107. [29] S. Siva, G. Venkatesh, A. Antony Muthu Prabhu, R.K. Sankaranarayanan, N. Rajendiran, Phys. Chem. Liq. 50 (2012) 434–452. [30] A. Antony Muthu Prabhu, R.K. Sankaranarayanan, G. Venkatesh, N. Rajendiran, J. Phys. Chem. B 116 (2012) 9061–9074. [31] G. Venkatesh, A. Antony Muthu Prabhu, N. Rajendiran, J. Fluorescence 21 (2011) 1485–1497. [32] A. Antony Muthu Prabhu, N. Rajendiran, J. Fluorescence 22 (2012) 1461–1474.
